JP2019501017A - Method for manufacturing conductive structure - Google Patents

Abstract

The present invention relates to a method for producing a conductive structure, in which nanofibers are applied onto a substrate together with a photocatalytic component, in particular by electrospinning, and a metal layer is deposited on the substrate by photolysis.
[Selection] Figure 1

Description

  The present invention relates to a method for producing a metal structure, in particular a conductive structure, and to a substrate of this kind and its use.

The fibers obtained by electrospinning have a very high aspect ratio, which is advantageous in applications that require a large surface area in addition to a low volume. For example, TiO ₂ nanofibers coated with silver nanoparticles have been used for surface enhanced Raman spectroscopy, antibacterial coatings, photocatalysis, and energy conversion. Conductive nanofibers have also been proposed as electrodes or for touch screens.

  At the same time, the known methods are often very complex and the resulting coating cannot be well structured.

  The problem addressed by the present invention is to identify a method by which metal structures based on nanofibers, in particular transparent conductive structures, can be produced.

  The above object can be achieved by the invention having the features of the independent claims described in the claims. Advantageous developments of these inventions are specified in the dependent claims. The expressions in all the claims recited in the claims are hereby incorporated by reference. These inventions include all conceivable combinations of the independent claims and / or the dependent claims, in particular all the mentioned independent claims and / or dependent claims.

The said subject is achieved by the manufacturing method of a metal structure. Hereinafter, each process of this method is demonstrated in detail. These steps need not necessarily be performed in the order specified, and the methods outlined below may further include unspecified steps. This method
a) providing nanofibers containing a photocatalytic component on a substrate;
b) contacting at least one metal structure precursor compound with nanofibers;
c) reducing at least one precursor compound to a metal structure by the action of electromagnetic radiation on the photocatalytic component;
including.

  In step c), a metal layer is typically formed. In this case, a metal layer in the context of the present invention is understood to mean a layer of metal. This type of layer may be conductive as long as it has an appropriate thickness, and this type of conductive layer is particularly preferred. Here, “conductive” does not necessarily mean the production of a structure that essentially constitutes a conductor track, and in principle, the production of dots from a conductive material also constitutes a conductive structure. And

  When nanofibers are used, a metal layer can be formed along the fibers, and the conductive structure can be made thinner. By the photocatalytic action of the fiber, selective reduction can be performed in this fiber. The precursor compound itself is easier to handle because it is negligible, if any.

  The substrate providing the nanofibers may be any material suitable for this purpose. Examples of suitable materials include metals or metal alloys, glasses, ceramics such as oxide ceramics, glass ceramics, plastics, and paper and other cellulosic materials. Of course, it is also possible to use a substrate having a surface layer made of the above-mentioned materials. The surface layer can be, for example, a metallized layer, an enamel layer, a glass layer, a ceramic layer, or a paint system.

Examples of the metal or metal alloy include steel including stainless steel, chromium, copper, titanium, tin, zinc, brass, and aluminum. Examples of the glass include soda lime glass, borosilicate glass, lead crystal glass, and silica glass. This glass may be, for example, plate glass, hollow glass such as a glass container, or experimental glass equipment. The ceramic may be, for example, a ceramic based on an oxide such as SiO ₂ , Al ₂ O ₃ , ZrO ₂ , or MgO, or a corresponding mixed oxide. Plastics can exist in the form of films as well as metals, examples of which are polyethylene, such as HDPE or LDPE, polypropylene, polyisobutylene, polystyrene (PS), polyvinyl chloride (PVC), polyvinylidene chloride, polyvinyl butyral. , Polytetrafluoroethylene, polychlorotrifluoroethylene, polyacrylate, polymethacrylate such as polymethyl methacrylate (PMMA), polyamide, polyethylene terephthalate (PET), polycarbonate, regenerated cellulose, cellulose nitrate, cellulose acetate, cellulose triacetate (TAC) ), Cellulose acetate butyrate, and hydrochloric acid rubber. The painted surface can be formed from a standard base coat or paint. In a preferred embodiment, the substrate is a film, particularly a polyethylene terephthalate film or a polyimide film. When manufacturing the structure directly on the surface, the surface must be able to withstand manufacturing conditions such as temperature.

The nanofiber contains at least one photocatalytically active component. This photocatalytically active component is a compound that directly reduces a metal ion in a metal complex to a metal without being decomposed by itself, and / or a compound that is indirectly reduced by oxidative aging of a metal complex or a further substance Is understood to mean. Products generated in the oxidation cause decomposition of the metal complex and reduction of metal ions in the complex. Photocatalyst material may be a ZnO or TiO _2, it is preferably TiO _2, more preferably anatase TiO _2.

  In a particularly preferred embodiment of the invention, the titanium dioxide is present as at least anatase titanium dioxide and amorphous titanium dioxide. The size of the crystallites (determined by X-ray diffraction) of the anatase titanium dioxide embedded in the amorphous titanium dioxide matrix is more preferably less than 20 nm, and still more preferably less than 10 nm. The fiber is composed of a composite of anatase type titanium dioxide and amorphous type titanium dioxide. The conversion of these titanium dioxides can be controlled by selecting the firing conditions.

It is particularly preferable that the fiber, particularly a fiber made of a composite of anatase type titanium dioxide and amorphous type titanium dioxide, has a specific surface area of at least 80 m ² / g, particularly preferably at least 90 m ² / g.

  The nanofibers preferably have an average length of more than 10 μm, particularly preferably an average length of more than 20 μm and more preferably an average length of more than 50 μm.

  In a preferred embodiment of the present invention, nanofibers are obtained by electrospinning.

  For this purpose, a composition containing a matrix material or a precursor thereof and a photocatalytic component or a precursor thereof is prepared.

  The composition is spun by electrospinning to obtain nanofibers.

  It may be necessary to treat the resulting fiber, for example to dry at a temperature below 200 ° C., in particular below 150 ° C.

  Immediately after electrospinning, it may be necessary to rest the fiber for at least 12 hours before further processing.

  It may be necessary to apply nanofibers to the final substrate.

  The nanofiber after electrospinning preferably has an average diameter of less than 1 μm, in particular less than 500 nm (determined by ESEM), in particular less than 400 nm. The fiber preferably has a circular cross section. The diameter is preferably 30 nm to 500 nm, particularly 50 nm to 350 nm.

  Prior to its use, the fiber may need to be heat treated above 300 ° C., in particular above 400 ° C. The temperature of the heat treatment is preferably 300 ° C to 800 ° C, particularly preferably 300 ° C to 600 ° C. The heat treatment time can be 1 minute to 5 hours. As a result, when titanium dioxide is used, anatase type titanium dioxide can be obtained.

  In one embodiment of the invention, the photocatalytically active component comprises nanoparticles, preferably nanoparticles produced by a non-hydrolyzed sol-gel process. For this purpose, the hydrolyzable titanium compound and / or hydrolyzable zinc compound is reacted with an alcohol and / or acid, preferably carbonic acid, preferably in a protective gas atmosphere. This reaction is preferably performed at a temperature of 10 ° C to 100 ° C, more preferably at a temperature of 15 ° C to 30 ° C. In one embodiment, the reaction can be performed at room temperature.

The hydrolyzable titanium compound is a compound represented by the formula of TiX ₄ in particular. In the formula, the hydrolyzable groups X may be the same or different, for example, hydrogen, halogen (F, Cl, Br, or I, especially Cl and Br), alkoxy (preferably C ₁ -C ₆ alkoxy) Particularly preferably, C ₁ -C ₄ alkoxy such as methoxy, ethoxy, n-propoxy, i-propoxy, butoxy, i-butoxy, sec-butoxy and tert-butoxy), aryloxy (preferably phenoxy, etc.) _C 6 _{-C 10} aryloxy), and acyloxy (e.g., acetoxy or propionyloxy _C 1 -C ₆ acyloxy oxy, etc.), or, alkylcarbonyl (preferably in _C 2 -C ₇ alkylcarbonyl) such as acetyl is there. Examples of halides include TiCl _4. The hydrolyzable radical X is more preferably an alkoxy group, and particularly preferably C ₁ -C ₄ alkoxy. Specific titanates include Ti (OCH ₃ ) ₄ , Ti (OC ₂ H ₅ ) ₄ , and Ti (n- or i-OC ₃ H ₇ ) ₄ .

In the case of a zinc compound, a zinc carbonate compound such as Zn (OAc) ₂ is one option.

  The alcohol and / or acid is usually a lower alcohol and an inorganic acid or carboxylic acid. Examples of such compounds include methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, and alkyl alcohols such as neopentanol, glycol, propane-1,3-diol, and Benzyl alcohol such as benzyl alcohol which may be substituted on the aromatic ring. Examples of carboxylic acids include formic acid, acetic acid, propionic acid, butyric acid, and oxalic acid. It is also possible to use mixtures of solvents. It is also preferred to use this compound as a solvent, i.e. obviously in excess. Examples of inorganic acids include hydrochloric acid, sulfuric acid, phosphoric acid, and nitric acid. These acids can be used as an aqueous solution or an alcohol solution. It may be necessary to aid hydrolysis by adding water.

  In order to obtain crystalline nanoparticles, it may be necessary to perform a heat treatment, preferably for example under a self-generated pressure. For this, the reaction mixture is treated in a closed vessel at a temperature of 50 ° C. to 300 ° C. for 2 hours to 48 hours.

  The obtained nanoparticles can be obtained by simple centrifugation and solvent removal.

  The nanoparticles preferably have an average diameter of less than 200 mm (determined by TEM), more preferably less than 100 mm, particularly preferably less than 50 nm.

  The nanoparticles may be doped, for example, to shift its absorption region to another spectral region.

  To this end, in the production of nanoparticles, suitable metal compounds, such as oxides, salts or complexes, such as halides, nitrates, sulfates, carboxylates (eg acetates), or Acetylacetonate can be used for dope. This compound must be appropriately soluble in the solvent used to produce the nanoparticles. A suitable metal may be any metal, but is particularly a metal selected from Groups 5 to 14 of the periodic table, lanthanoids, and actinoids. Here, these families are listed according to the new IUPAC system shown in Roempp Chemie Lexikon (9th edition). This metal can be formed in the compound in a suitable oxidation precursor.

Examples of suitable metals for the metal compounds include W, Mo, Zn, Cu, Ag, Au, Sn, In, Fe, Co, Ni, Mn, Ru, V, Nb, Ir, Rh, Os, Pd and Pt are mentioned. W (VI), Mo (VI), Zn (II), Cu (II), Au (III), Sn (IV), In (III), Fe (III), Co (II), V (V), And it is preferable to use a metal compound of Pt (IV). Very good results are obtained especially in the case of W (VI), Mo (VI), Zn (II), Cu (II), Sn (IV), In (III) and Fe (III). . Preferable specific examples of the metal compound include WO ₃ , MoO ₃ , FeCl ₃ , silver acetate, zinc chloride, copper (II) chloride, indium (III) oxide, and tin (IV) acetate.

  The ratio of the metal compound to the titanium compound or zinc compound also depends on the metal used and its oxidation state. The metal molar ratio (Me / Ti (Zn)) of the metal compound to titanium / zinc of the titanium compound or zinc compound is 0.0005: 1 to 0.2: 1, preferably 0.001: 1 to 0.005: 1. It is common to use a ratio of 0.1: 1, more preferably 0.005: 1 to 0.1: 1.

  The obtained nanoparticles may be subjected to surface modification, for example, in order to give affinity to the matrix material used therein. For example, it is possible to create a nanoparticle concentration gradient for the fiber by surface modification with a fluorinated group. Nanoparticles accumulate on the surface of the fiber.

  In another embodiment of the invention, the composition comprises a precursor compound of a photocatalytically active component. This precursor compound is, for example, the hydrolyzable compound for nanoparticles described above. First, it may be necessary to convert this compound to a sol. This can be achieved, for example, by adding an acid such as acetic acid or hydrochloric acid.

  The composition also contains at least one matrix material or at least one precursor thereof. This can be an organic matrix forming material, an inorganic matrix forming material, or an organically modified inorganic matrix forming material, in particular an inorganic sol or an organically modified inorganic hybrid material. It is preferable to include. Examples include at least one glass-forming element M, or optionally organically modified oxides, hydrolysates and (poly) condensates of at least one ceramic-forming element M. In particular, the element M is an element M selected from Group 3 to Group 5 and / or Group 12 to Group 15 of the periodic table, and preferably Si, Al, B, Ge, Pb, Sn, Ti, Zr, V, and Zn, or a mixture thereof. A proportion of periodic table Group 1 and Group 2 elements (eg, Na, K, Ca, and Mg) and Periodic Table Group 5-10 elements (eg, Mn, Cr, Fe, and Ni) or lanthanides can also be present in the oxides, hydrolysates or (poly) condensates. This can be, for example, a sol containing Ti, which can optionally also be a precursor of the photocatalytically active component.

  In the case of an organic matrix material, it has an organic polymer and / or oligomer, preferably a polar group such as a hydroxyl group, primary, secondary, or tertiary amino group, carboxyl group, or carboxylic acid group. Organic polymers and / or oligomers can be used. Typical examples include polyvinyl alcohol, polyethylene oxide, polyvinyl pyrrolidone, polyacrylamide, polyvinyl pyridine, polyallylamine, polyacrylic acid, polyvinyl butyral and other polyvinyl acetate, polymethylmethacrylic acid, starch, gum arabic, and polyethylene. -Polyvinyl alcohol copolymer, polyethylene glycol, polypropylene glycol, and other polymer alcohols such as poly (4-vinylphenol), or monomers or oligomers derived therefrom. Of these, polyvinylpyrrolidone (PVA) is preferable.

Organic polymers having a molecular mass (average molecular weight; M _w ) exceeding 200,000 g / mol and up to 300,000 g / mol are preferred.

  The composition may include at least one solvent. All components must be soluble or dispersible in the solvent. The solvent can be, for example, an alcohol such as methanol, ethanol, or isopropanol. One or more solvents having a boiling point below 150 ° C., in particular below 100 ° C. are preferred.

  Additives such as surfactants, antioxidants, plasticizers and the like can also be present.

  The viscosity of the composition can be adjusted according to the electrospinning conditions.

  Although depending on the composition, the content of the matrix component when the matrix component is an organic matrix component is 2% by weight to 15% by weight, particularly 2% by weight to 10% by weight, based on the composition.

  In particular, if the composition includes a hydrolyzable compound, it may be necessary to mix the composition for 1 hour to 72 hours prior to electrospinning.

  Preferred conditions for electrospinning include a voltage of 8 kV to 20 kV and a spinning dope flow rate of 0.3 mL / h to 1.5 mL / h. The distance from the surface where the fibers are collected is preferably 10 cm to 30 cm. It is preferable to use a needle having an inner diameter of 0.4 mm to 2 mm.

  In one embodiment of the present invention, the fiber is manufactured by electrospinning using a concentric ring nozzle. This type of nozzle has a central opening and a surrounding annular opening. As such, the fiber can be made from two different compositions. One of the two different compositions is the composition that forms the core of the fiber (center ring nozzle), and the other is the composition that forms the shell of the fiber (the surrounding ring opening). Thereby, for example, it becomes possible to produce a fiber containing the photocatalytic component only in the shell and not in the core.

In a preferred embodiment (i) of the invention, the spinning composition comprises nanoparticles having photocatalytic activity, preferably TiO ₂ , more preferably anatase TiO ₂ and at least one organic polymer, preferably PVA. Containing. For this purpose, it is preferred to use nanoparticles produced as described above.

  In a further preferred embodiment (ii) of the present invention, the spinning composition comprises a precursor of a photocatalytic component, in particular a hydrolyzable titanium compound or a condensate thereof, and at least one organic polymer as described above. And / or an oligomer. This precursor is, for example, the hydrolyzable compound for nanoparticles described above. First, it may be necessary to convert this compound to a sol. This can be achieved, for example, by adding an acid such as acetic acid or hydrochloric acid.

  In a further preferred embodiment (iii) of the present invention, the composition for the fiber shell contains nanoparticles having photocatalytic activity, and the composition for the fiber core comprises at least one organic polymer. Containing. In this case, the fiber is obtained by electrospinning using a coaxial ring nozzle. In the subsequent step, the polymer can be removed, for example, by solvent and / or calcination. Thereby, the tube which has photocatalytic activity is obtained.

  In a further preferred embodiment (iv) of the present invention, the composition for the shell contains nanoparticles having photocatalytic activity, and the composition for the core contains at least one precursor compound of the photocatalytic component. contains.

  In a specific embodiment of the present invention according to (ii), the precursor compound is a titanium dioxide precursor compound, and the manufactured fiber is heat-treated before use. The heat treatment conditions are selected so that the precursor compound becomes a complex of anatase titanium dioxide and amorphous titanium dioxide, and in particular, the crystallites of anatase titanium dioxide are embedded in the matrix of amorphous titanium dioxide. It is preferable. This is achieved in particular by firing temperatures above 400 ° C. and below 500 ° C., preferably above 420 ° C. and below 480 ° C., more preferably above 430 ° C. and below 470 ° C., particularly preferably from 440 ° C. to 460 ° C. Is done. The heat treatment time is preferably 30 minutes to 4 hours. In particular, at a temperature of 430 ° C. to 470 ° C., a fiber containing anatase titanium dioxide crystallites in a matrix of amorphous titanium dioxide is obtained at the same time as the porosity is particularly high. This is particularly beneficial for uniform metallization. In this way, a conductive structure can be obtained. The heating rate is preferably 1 ° C / min to 3 ° C / min.

  A heat treatment can be performed on the final substrate.

  In the next step, a precursor composition containing at least one precursor compound for the metal layer is applied onto the substrate. The precursor composition can be applied by using conventional methods such as dipping, rolling, knife coating, flow coating, stretching, spraying, spinning, or painting. The precursor composition is typically a solution or suspension of the at least one precursor compound. This solution may comprise a mixture of a plurality of precursor compounds. An auxiliary agent such as a reducing agent or a wetting auxiliary agent may be further present in the solution.

  The precursor compound is preferably a metal complex. The metal complex has at least one metal ion or metal atom and at least one ligand. The metal is, for example, copper, silver, gold, nickel, zinc, aluminum, titanium, chromium, manganese, tungsten, platinum, or palladium. In a preferred embodiment, the precursor compound is a silver complex, a gold complex, or a copper complex, and more preferably a silver complex. The precursor compound may contain a plurality of types of metals, or may contain a mixture of metal complexes.

The ligand used is usually a chelate ligand. This ligand is a compound which can form a particularly stable complex and has a plurality of hydroxyl groups and / or amino groups. Compounds having a molecular weight of less than 200 g / mol are preferred, and compounds having at least one hydroxyl group and at least one amino group are particularly preferred. Examples of possible compounds include 3-aminopropane-1,2-diol, 2-amino-1-butanol, tris- (hydroxymethyl) aminomethane (Tris), NH ₃ , nicotinamide, and 6-amino. Hexanoic acid is mentioned. It is also possible to use mixtures of these ligands. In the case of a suitable silver complex, the ligand is preferably Tris.

The precursor composition is preferably a solution of the precursor compound. Useful solvents may be any suitable solvent, such as water or alcohols such as methanol, ethanol, n-propanol, or i-propanol. It is also possible to use a mixture of solvents, preferably a mixture of water and ethanol. As a suitable mixing ratio, the ratio of H ₂ O: alcohol, preferably H ₂ O: ethanol is 50 wt%: 50 wt% to 20 wt%: 80 wt%.

  In addition, the precursor composition may further contain an auxiliary agent such as a surfactant or a reducing auxiliary agent.

  The precursor composition can be applied onto the substrate by a desired method. The precursor composition is applied so that the photocatalytic activity of the nanofibers can induce reduction of metal ions to metal, either directly or indirectly. This is typically achieved by applying the precursor composition directly to the nanofibers.

  The precursor composition can be applied using standard methods such as dipping, spraying, rolling, knife coating, flow coating, stretching, spraying, spinning, or painting. .

For example, the precursor composition can be applied through a frame placed on a substrate, and the precursor composition is introduced into a space surrounded by the frame formed by placing the frame. . The frame may be made of an elastic material, and may have any shape as long as it has a desired shape, and is typically a rectangular frame. Frame, for example, to surround the substrate, side length 1Cm～25cm, the area of the area of ^{1cm 2 ~625cm} 2. The thickness of the precursor composition to be applied is determined by the height of the frame on the substrate. The frame can have a height of 25 μm to 5 mm, preferably 30 μm to 2 mm.

  In the next step, the metal ion of the precursor compound is reduced to a metal by the action of electromagnetic radiation on the photocatalytic component of the fiber. Thereby, a metal layer is formed. Electromagnetic radiation is radiation of a wavelength that excites the photocatalytic component. The irradiation can be performed by using a surface radiation source such as a lamp or a laser. It is preferred to use radiation with a wavelength in the visible or ultraviolet (UV) region of the electromagnetic spectrum, preferably less than 500 nm, for example 200 nm to 450 nm, or 250 nm to 410 nm. Radiation with a wavelength of less than 400 nm is preferred.

  The light source used may be any suitable light source. Examples of the light source include a mercury lamp and a xenon lamp.

The light source is disposed at an appropriate distance from the substrate to be exposed. The distance can be, for example, 2.5 cm to 50 cm. The intensity of the radiation in the spectral region of 250nm~410nm ^may be a ^{30mW / cm 2 ~70mW / cm 2} .

  Irradiation should be as perpendicular as possible to the surface to be exposed.

  Irradiation is performed for a time sufficient to form the metal layer. Here, the irradiation time is determined by the coating, the type of initiator, the type of lamp, the wavelength region used, and the irradiation intensity. If it is desired to make a conductive structure, it may be necessary to lengthen the irradiation time. The irradiation time is preferably 5 seconds to 30 minutes, and more preferably 20 seconds to 15 minutes.

  When a laser is used for irradiation, for example, an argon ion laser (351 nm) can be used at 10 mW. In this case, the laser beam is guided in a focused and parallel manner over the substrate to be irradiated at a speed of 2 mm / second.

  In a further embodiment of the invention, the substrate is further processed after irradiation and reduction of the precursor compound. For example, unreduced excess precursor composition can be removed by rinsing the surface with deionized water or other suitable material. Next, the coated substrate can be dried by oven heating, compressed air, and / or room temperature drying or the like.

  Irradiation can be repeated, for example, twice, three times, or four times.

  In a preferred embodiment, after the first irradiation, the substrate is cleaned and then irradiated at least once more. This can reduce non-selective deposition on the surface.

  For example, a layer may be further provided to protect the coated surface from oxidation, water, or UV light.

  In a preferred embodiment of the present invention, structuring is achieved by application and / or reduction of the precursor composition. In the context of the present invention, this is understood to mean the construction of a spatially limited metal structure and is possible in various ways. First, only a specific region of the substrate can be covered with nanofibers. It is also possible to apply the precursor composition only to a specific region. It is also possible to limit the action of electromagnetic radiation to a specific area. Of course, a combination of these methods can also be used. For example, the precursor composition can be applied to the entire area and then exposed through a mask. Similarly, it is naturally possible to selectively apply the precursor composition and then expose the entire area.

  In particular, when using electrospinning, the spun fibers can be applied to a structured substrate, particularly a substrate having elongated recesses. Depending on its length, the fibers are ordered along the recess.

  After this process, additional layers can be provided, for example, to protect the coated surface of the substrate from ultraviolet radiation.

  The structure provided by the structuring is not limited in practice. For example, a connection structure such as a conductor track can be provided, and a dot-like structure can also be provided. In order to provide good resolution, this process can provide invisible conductive dots on the film. This is very important in the production of touch screen surfaces.

  Further, the present invention provides a method for producing a composite fiber containing anatase-type titanium dioxide and amorphous-type titanium dioxide, which is not metallized and has photocatalytic activity, as in the embodiment according to (ii) above. About. Here, as described above, the spinning composition contains at least one hydrolyzable titanium compound or a condensate thereof and at least one organic polymer and / or oligomer. This hydrolysable titanium compound is, for example, the above-mentioned hydrolysable titanium compound for nanoparticles. First, it may be necessary to convert this compound to a sol. This can be achieved, for example, by adding an acid such as acetic acid or hydrochloric acid.

  The spinning composition is spun by electrospinning and the fiber is applied to the substrate. Then, as described above, the heat treatment is performed at a temperature higher than 400 ° C. and lower than 500 ° C., preferably higher than 420 ° C. and lower than 480 ° C., more preferably higher than 430 ° C. and lower than 470 ° C. . The heat treatment time is preferably 30 minutes to 4 hours. In particular, at a temperature of 430 ° C. to 470 ° C., a fiber containing anatase titanium dioxide crystallites in a matrix of amorphous titanium dioxide is obtained at the same time as the porosity is particularly high. This is particularly beneficial for uniform metallization. In this way, a conductive structure can be obtained. The heating rate is preferably 1 ° C / min to 3 ° C / min.

  The fiber thus obtained is particularly advantageous for the method for producing a metal structure of the present invention.

  The present invention also relates to a composite fiber obtained by the method of the present invention.

  Moreover, this invention relates to the board | substrate provided with at least 1 sort (s) of the composite fiber obtained by the method of this invention.

  The present invention also relates to a coated substrate obtained by the method of the present invention. Such a substrate is characterized by a layer having photocatalytic activity comprising nanofibers having photocatalytic activity. This layer has a thickness of 50 nm to 200 μm. The thickness of the layer is preferably 100 nm to 1 μm, more preferably 50 nm to 700 nm.

  The fiber preferably contains a composite composed of anatase-type titanium dioxide and amorphous-type titanium dioxide, particularly a composite obtained by the method of the present invention.

  In a further embodiment of the invention, the fiber is at least partially metallized. The metals useful here are in particular copper, silver, gold, nickel, zinc, aluminum, titanium, chromium, manganese, tungsten, platinum or palladium, preferably silver or gold. These metals may be individual particles. The fiber is preferably coated with the metal, which can be detected by TEM. More preferably, the coating on the substrate is conductive, which means a structure having a resistance of less than 3 MΩ, preferably 2 MΩ, most preferably 1 MΩ in at least one direction at a distance of 5 mm. Understood. The manufactured structure preferably has anisotropic resistance due to its fiber structure. Anisotropic resistance means that the resistance varies at least 2 times, at least 10 times, in particular 100 times, depending on the direction of measurement.

  The thickness of the metal layer can be up to 200 mm. The thickness of the layer is preferably 10 nm to 100 nm, more preferably 5 nm to 50 nm.

  In a particularly advantageous embodiment of the invention, the coating on the substrate is at least partially transparent, in particular totally transparent. This is because the coverage by the fiber after electrospinning in the coated region on the surface of the substrate is less than 20% of the coated surface region of the substrate, in particular 10% to 20%, preferably 10% to 15%. Can be achieved. This can be achieved, for example, by electrospinning time. The coverage can be determined by measuring average transmittance and haze as a function of electrospinning time.

  The fiber coating preferably reduces the average transmittance by at most 5%.

  In a development of the invention, the substrate is structured by structural elements having a size of less than 50 μm, preferably less than 10 μm. This structural element may provide a metallic region and / or a non-metallic region. More preferably, the metal structure is a metal coating of nanofibers.

  In a particularly advantageous development of the invention, the coated substrate comprises a metal structure that is at least partially transparent. This can be achieved by applying to the transparent substrate a structure having a resolution of less than 20 μm, preferably less than 10 μm.

  The coated substrate obtained by the method of the present invention can be used for many applications.

  First, the method is suitable for applying a reflective metal layer to a surface. These coated substrates can be used, for example, as a reflective layer in holographic applications.

  A particular advantage of the present invention is in the manufacture of conductive structures. These conductive structures are suitable as conductor tracks in electronics applications, especially in touch screen displays, in solar collectors, in displays, as RFID antennas or in transistors. Thus, the conductive structure is suitable as an alternative in products that have been produced so far, based on ITO (indium tin oxide), for example in TCO coatings (TCO: transparent conductive oxide). In particular, it is possible to obtain a transparent structure and a structure having anisotropic resistance.

  This structure can alternatively be used in the transistor field.

  Further details and features will become apparent from the following description of preferred embodiments in conjunction with the dependent claims. In this context, each feature itself, or some of them, can be implemented in combination with each other. Means for solving the problem is not limited to these examples. For example, the specified range always includes all intermediate values not explicitly specified and all possible subintervals.

  An example is shown in the schematic diagram. The same reference signs in the individual drawings indicate elements that are the same or that have the same function or that correspond to each other in terms of their function. Specifically, the figure shows the following.

a) Distribution of fiber diameter immediately after manufacture (“fiber diameter” (nm) vs. pulse (count)). b) ESEM (environmentally controlled scanning electron microscope) image of the fiber after (i). a) Fiber diameter distribution (“fiber diameter” (nm) vs. pulse (count)). b) ESEM (environmentally controlled scanning electron microscope) image of the fiber after (ii). a) Fiber diameter distribution after production (“as-spun”), after 5 minutes firing at 500 ° C. (5 minutes firing), and after 30 minutes firing at 500 ° C. (30 minutes firing) (“fiber It is a figure which shows a "diameter" (nm)). b) ESEM image of the sample after baking for 30 minutes. EDS spectrum (energy (keV) vs. strength) of the fiber after production ("as-spun", lower graph), after 5 minutes firing (middle graph), and after 30 minutes firing (upper graph) FIG. It is a figure which shows the XRD spectrum of the sample after baking for 5 minutes (lower graph) and after baking for 30 minutes (upper graph). The anatase signal is 25.32 °, 38 °, and 48.01 °. It is a figure which shows size distribution (nm range) of the diameter of the silver particle formed on the fiber after irradiation for 3 minutes (A), after irradiation for 5 minutes (B), and after irradiation for 7 minutes (C). An ESEM image of the TiO ₂ mat after UV exposure for 4 minutes in the presence of AgNO ₃ -Tris complex (left side) and 30% coverage on glass after UV exposure for 4 minutes under the same conditions. It is an ESEM image (right side) of the fiber. It is a figure which shows the result of having measured the diameter distribution of the manufactured fiber by TEM. It is an ESEM image of a sample obtained at a firing temperature of 450 ° C. and a) FD 10 cm, CT 30 minutes, b) FD 20 cm, CT 30 minutes, c) FD 10 cm, CT 60 minutes, and d) FD 20 cm, CT 60 minutes. It is a TEM image showing the fiber baked at (a) 450 degreeC, 60 minutes, (b) 475 degreeC, 60 minutes, and (c) 500 degreeC, 60 minutes. In each case, the FD is 10 cm. It is a Raman spectrum showing the fiber baked at 450 degreeC, 475 degreeC, and 500 degreeC. It is a figure which shows the gas adsorption analysis plot of the sample baked at 450 degreeC (left side, FD20cm), 475 degreeC (middle, FD15cm), and 500 degreeC (right side, FD15cm) (in each case CT is 60 minutes). . The X axis indicates the partial pressure P / P0, the Y axis in each case indicates the adsorption amount (cc / g STP), the square symbol indicates the adsorption amount, and the circle symbol indicates the desorption amount. It is the image of the fiber after depositing silver on the fiber a) baked by 450 degreeC, FD20cm, CT60 minutes, and b) 475 degreeC, FD20cm, CT60 minutes. It is the figure which calculated | required the coverage as a function of deposition time.

  Various strategies were used for the nanofiber electrospinning process.

(I) A TiO ₂ nanocrystal produced by a hydrothermal method is introduced into a polymer compound and electrospun to obtain nanofibers.
(Ii) Anatase-containing fiber is prepared from TiO ₂ obtained from a titanium alkoxide precursor compound and a polymer spinning compound.
(Iii) A fiber having a polymer core and a shell that is a TiO ₂ crystal converted by a hydrothermal method is obtained by coaxial electrospinning, and after heat treatment, the polymer is washed to obtain an anatase-type titanium dioxide tube.
(Iv) A fiber having a core that is a titanium alkoxide and a shell that is a TiO ₂ crystal produced by a hydrothermal method is obtained by coaxial electrospinning.

  All the substrates are used to photochemically deposit silver.

Experiment relating to (i) Ultrafine fibers were obtained by electrospinning an aqueous sol of TiO ₂ nanocrystals fired hydrothermally. For this purpose, titanium tetraisopropoxide was mixed with isopropanol and hydrochloric acid to obtain a TiO ₂ network. To this, water and isopropanol were added to obtain a sol. Next, the sol was introduced into a fixed volume autoclave and heated to 250 ° C. to obtain anatase TiO ₂ . The resulting nanocrystals were redispersed and optionally surface modified. High molecular weight polyvinylpyrrolidone (Mw = 1300,000 g / mol, hPVP) was added to this composition to a content of 4% by weight (relative to the total composition).

The obtained fiber is shown in FIG. The fiber diameter was very small and had a slightly rough surface. This suggests that the TiO ₂ particles are located in the fiber.

Experiment related to (ii) Anatase-containing nanofibers were obtained as follows. Titanium tetraisopropoxide (Ti (O-iPr) ₄ ) was gradually hydrolyzed at a ratio of 0.25: 1: 1 in a mixture of acetic acid and ethanol to obtain a sol. High molecular weight polyvinylpyrrolidone (Mw = 1300,000 g / mol, hPVP) was added to the sol, and ethanol was added to completely dissolve the sol. The content of hPVP was 9% by weight based on the entire composition.

  A composition having a polymer concentration of 5% by weight was also prepared by changing the amount of ethanol added.

The sol was allowed to stand for 24 hours (optionally with slight agitation) and electrospun under the following conditions:
A 21G spinneret was installed at a distance of 15 cm perpendicular to the ground copper plate coated with aluminum stays. The flow rate of the spinning dope was set to 0.82 mL / h or 0.5 mL / min to 0.8 mL / min (temperature 21 ° C., air humidity 43%) using a syringe pump. Spun fibers were formed at a voltage of 18 kV to 21 kV, in particular 18 kV to 20 kV.

  For optical testing, a 3 cm × 3 cm glass plate was held under the spinneret (at a distance of 10 cm to 20 cm) for varying times (1 and 15 seconds). FIG. 2 shows a typical distribution of fiber diameters of the fibers. The fiber has an average diameter of 103 nm ± 53 nm and exhibits a smooth cylindrical form.

  In order to apply individual fibers to the surface, the fiber application was performed for 12-15 seconds while moving the glass plate (5 wt%, 0.5 mL / min to 0.8 mL / min, 21 gauge, 18 kV to 20 kV, FD 10 cm to 20 cm). Thereby, 12% to 15% of the glass surface was covered with the fiber. The fibers are 20 μm to 100 μm apart, and after firing, all fibers have a maximum diameter of less than 500 nm.

  After spinning, the fiber applied on the substrate was heated at 120 ° C. for 12 hours to remove water and solvent. It can be removed at 80 ° C. for 12 to 24 hours.

  Then, it baked at 500 degreeC (a heating rate and a cooling rate are 2.66 degreeC / min, respectively). In order to investigate the optimum formation conditions of anatase titanium dioxide, two different retention times of 5 minutes and 30 minutes were examined. The fiber obtained with a holding time of 30 minutes later showed improved coverage with silver. All examples shown in FIGS. 1 to 6 were baked at 500 ° C. for 30 minutes. In the case of other samples, the firing temperature and time are determined respectively. After heating, the firing temperature was maintained for a specified time.

  The sample was cooled to room temperature over at least 3 hours.

The change of the fiber diameter by baking is shown in FIG. The fibers are clearly thinner and the size distribution is narrower. The EDS spectrum shown in FIG. 4 clearly shows that the peaks at 0.277 keV and 0.525 keV corresponding to the carbon and oxygen Kα rays in PVP ([C ₆ H ₉ NO] _n ) are reduced. It is shown. The peak at 4.508 keV corresponds to the Kα of titanium. If calcination is prolonged, the carbon reacts to CO ₂ and oxygen forms TiO ₂ . The Ti Lα at 0.452 keV is also evident in the spectrum. The low carbon absorption is believed to be due to the fixed band of the sample.

  The fact that anatase-type crystals are produced by firing is also shown by X-ray diffraction (FIG. 5).

  FIG. 6 shows the size distribution of silver nanoparticles formed on the surface at various irradiation times.

  For the metallization in the following examples, an aqueous silver nitrate solution containing a Tris complex was used as a precursor for the metal layer. The composition was freshly prepared and dispensed onto the fiber applied to the glass plate and then waited 30 seconds. Then, after irradiating the fiber with UV light (1000 W) for 3 minutes, the sample was washed, and again irradiated with UV light (1000 W) for 2 minutes. Washing reduces the spontaneous deposition of silver on the glass surface.

The left side of FIG. 7 shows a fiber mat (baked at 500 ° C. for 30 minutes) after exposure for 4 minutes in the presence of AgNO ₃ -Tris complex. The silver coating is metallic, has contact resistance and is conductive (11.8 Ωcm). The image fiber on the left is also exposed for 4 minutes under the same conditions, but is incompletely silver coated and non-conductive.

  For further experiments, as possible factors, the influence of the distance before the substrate collision in electrospinning (“flying distance”, FD), firing time (CT), and firing temperature was examined. Each fiber was made from three different starting material batches.

  The transmittance of all the fibers produced on the glass was measured. The results are shown in Table 1. In the sample display, FD represents the flight distance, and CT represents the firing time (minutes). Therefore, FD10CT60 means a firing time of 60 minutes at a flight distance of 10 cm. In all cases where the fiber coverage on the glass surface is 15%, there is no apparent decrease in transmittance.

  When the coverage by the fiber on the glass surface is 12% to 15%, a decrease in transparency of up to 1% is measured compared to untreated glass, and after silver deposition, up to 2.5% Decrease is measured.

  The result of obtaining the coverage is shown in FIG. For this, transmittance or haze was measured as a function of electrospinning time. The numbers in parentheses indicate the measured transmittance and haze.

  FIG. 8 shows the flight distance (upper X axis indicates 10 cm or 20 cm), firing time (middle stage number indicates 30 minutes or 60 minutes), and firing temperature (these flight distances arranged above). The distribution of the diameters of the fibers produced as a function of 450 ° C, 475 ° C, and 500 ° C) is shown for the four combinations of distance and firing time. Samples spun at a 10 cm flight distance have a broader distribution due to the bimodal distribution of very thin and thicker fibers (eg, FIG. 9a). Fibers fired at 450 ° C. have less shrinkage than fibers fired at higher temperatures. An image of such a fiber is shown in FIG. The width of the figure corresponds to 1.25 μm. In order to obtain the diameter, the diameters of a large number of fibers in the fiber mat produced under the above conditions were measured. The fiber has a circular diameter.

  FIG. 10 shows TEM images of fibers at various firing temperatures. As the temperature increases, the crystallinity of the fiber increases.

FIG. 10 shows TEM images of the fiber after firing at various temperatures. As the firing temperature increases, the proportion of crystalline titanium dioxide, that is, the size of the crystalline structure, increases significantly. This is also apparent from the Raman spectrum shown in FIG. The smaller the amplitude and the smaller the peak width, the lower the crystallinity, that is, the nanocrystal. The peak at 450 ° C is much smaller than that at 475 ° C or 500 ° C. And the sample obtained at 450 degreeC shows a characteristic background fluorescence, and the peak with respect to O-Ti- _OB1g and O-Ti- _OA1g / _B1g is very unclear. This suggests that there is anatase-type titanium dioxide in the expanded Ti-O-Ti network in this fiber. Therefore, in the case of fibers fired at 450 ° C., there is a composite of amorphous titanium dioxide and crystalline titanium dioxide. Specifically, amorphous titanium dioxide is characterized by a clearly high porosity.

The high porosity is also shown in the gas adsorption capacity (FIG. 12). In the case of fibers fired at 450 ° C., a specific surface area (SSA) of 102 m ² / g (left side of FIG. 12) was measured, whereas fibers fired at 475 ° C. and 500 ° C. were 66 m ² each. / G (middle of FIG. 12) and 52 m ² / g (right side of FIG. 12).

The above AgNO ₃ / Tris complex was used for the following silver precipitation experiments. After reduction, the sample was washed and dried for 2 hours, and the transmittance was measured before and after metallization. The results are shown in Table 2. Metallization reduces the transmission by 1% to 4%, but for most samples the reduction is only around 1%.

  All samples fired at 450 ° C. were able to measure conductivity. For this purpose, a silver paste was applied to both ends of the glass for contact connection, and the conductivity was measured. The distance between the contacts was 5 mm. Anisotropic resistance was obtained due to the fiber shape of the sample. The results are shown in Table 3. The resistance also depends on how many fibers touch the contact.

  FIG. 13 shows two different metallization samples. FIG. 13a shows a sample metallized fiber (400 ° C., FD 20 cm, CT 60 min) showing conductivity, and FIG. 13b shows a sample metallized fiber (475 ° C., FD 20 cm, CT 60 min) showing no conductivity. . In FIG. 13a, it is clear that silver is deposited so as to form a shell around the fiber, thereby providing conductivity. In FIG. 13b, only larger individual silver particles are formed under the same conditions, but no conductivity is obtained by these particles. It is believed that the composite of amorphous titanium dioxide and atase titanium dioxide present in the fiber of FIG. 13a results in the formation of a metallic silver shell.

  None of the samples fired at only 400 ° C. exhibited electrical conductivity.

Claims (16)

a) providing nanofibers containing a photocatalytic component on a substrate;
b) contacting at least one metal structure precursor compound with the nanofibers;
c) reducing the at least one precursor compound to a metal structure by the action of electromagnetic radiation on the photocatalytic component;
A method for producing a metal structure, comprising:   The method according to claim 1, characterized in that the nanofibers are obtained by electrospinning.   The method according to claim 1, wherein the photocatalytic component comprises titanium dioxide.   The method according to claim 1, wherein the titanium dioxide is present as at least anatase titanium dioxide and amorphous titanium dioxide. The method according to claim 4, wherein the fiber has a specific surface area of at least 80 m ² / g.   The method according to claim 1, wherein the precursor compound is a silver complex, a gold complex, or a copper complex.   The method according to any one of claims 1 to 6, characterized in that the nanofibers have an average length of more than 10 m. A method for producing a composite fiber containing anatase-type titanium dioxide and amorphous-type titanium dioxide and having photocatalytic activity,
a) preparing a spinning composition containing at least one hydrolyzable titanium compound or a condensate thereof and at least one organic polymer and / or oligomer;
b) electrospinning the composition;
c) heat-treating the obtained fiber at more than 400 ° C. and less than 500 ° C .;
Manufacturing method.   The method according to claim 8, wherein the heat treatment in the step c) is performed at a temperature higher than 420 ° C. and lower than 480 ° C. 9.   A composite fiber obtained by the method according to claim 8 or 9.   A coated substrate comprising at least one composite fiber according to claim 10.   The coated substrate obtained by the method as described in any one of Claims 1-7 or Claim 8 and 9.   13. A coated substrate according to claim 11 or 12, characterized in that it has an at least partially transparent appearance.   The coated substrate according to claim 11, wherein the coating is conductive.   The coated substrate according to claim 14, wherein the coating has anisotropic resistance.   Use of a substrate according to any one of claims 11 to 15 as a conductor track in electronics applications, in a touch screen display, in a solar collector, in a display, as an RFID antenna or in a transistor.